Let us first calculate the probability of the events A and B from the given data. P(A)=1−P(ovA) = 1 − 0.4 = 0.6 Similarly, P(B)=1−P(B) = 1 − 0.3 = 0.7 It is already given that P(A ∪ B) = 0.9. Therefore, the probability of the intersection is given as follows: P(A ∩ B) = P(A) + P(B) − P(A ∪ B) = 0.6 + 0.7 − 0.9 = 1.3 − 0.9 = 0.4 Now we will calculate the probability of union of complimentary events as follows: P(A∪B)=P(A∩B) = 1 − P(A ∩ B) = 1 − 0.4 = 0.6 Therefore, the required probability is 0.6.